Solid propellants for rocket motors, solid explosives or the like contain energetic solids, including fuel particulates and oxidizer particulates, distributed throughout a polymeric binder. Among binders in common use in high energy formulations are those formulated from polyethylene glycol (PEG), polycaprolactone (PCP), and PEG/PCP mixtures. These binders are commonly plasticized with nitrate esters, such as nitroglycerine (NG), which enhance elastomeric properties of the polymers and further contribute substantially to the energy of the binders and the propellant or explosive compositions as a whole. Because the polymeric binders themselves have relatively low energies, efforts are continually made to develop more energetic binders.
It has been proposed to prepare binders by polymerizing cyclic ethers having from 2 to 4 carbon atoms in the ring plus energetic pendant groups and then curing the polyethers, for example, with isocyanates and cross-linking agents. Examples of such polyethers and methods of preparing the same are described in U.S. Pat. No. 4,483,978, the teachings of which are incorporated herein by reference. The '978 patent is specifically directed to polyethers having pendant nitro, nitrate and azido groups.
A continuing problem with polyether-based binders has been compatibility with nitrate ester plasticizers. In order to have sufficient energy for many propellant or explosive applications, the binders must stably immobilize substantial amounts of high-energy nitrate ester plasticizers, the desired weight ratio of plasticizer to polymer typically being at least about 2.0:1 and commonly at least about 2.5:1. If the binder is insufficiently miscible with nitrate ester plasticizers, the plasticizers will weep or exude from the binder.